CAVENDISH, Lord FREDERICK (1729–1803), field-marshal, third son of William, third duke of Devonshire, K.G., was born in August 1729. He entered the army as an ensign in the 2nd or Coldstream guards in 1750, and was promoted lieutenant and captain on 17 March 1752, captain and lieutenant-colonel on 3 May 1756, and colonel on 7 May 1758. He was elected M.P. for Derbyshire on 27 June 1751, in the room of his elder brother, the Marquis of Hartington, who was summoned to the House of Lords as Lord Cavendish of Hardwick, in his father's barony, and for Derby in 1754, a seat which he held without intermission till 1780. He was a most enthusiastic soldier, and with three other young officers, Wolfe, Monckton, and Keppel, made a compact on the outbreak of the seven years' war not to marry until France was conquered. Family influence secured his rapid promotion, and in April 1757 he proceeded to Germany as aide-de-camp to the Duke of Cumberland, and served the campaign of that year there. In September 1758 he accompanied the Duke of Marlborough in his ludicrous expedition against St. Malo as aide-de-camp, and was taken prisoner at the affair of St. Cas. He at first refused to go on parole, on the ground that his duty as a member of parliament would make it necessary for him to vote the supplies for further war against France; but the Duc d'Aiguillon overruled his objections, and said, ‘Let not that prevent you, for we should no more object to your voting in parliament than to your begetting children lest they should one day fight against France.’ In 1760, after his exchange had been arranged, he went to Germany again as brigadier-general, and held command of a brigade of infantry in the army of Prince Ferdinand of Brunswick till the conclusion of the war in 1763. In 1759–60 he was colonel 67th regiment. On 30 Oct. 1760 he was made colonel of the 34th regiment, a command which he held for thirty-seven years, and on 7 March 1761 he was promoted major-general. He succeeded to the beautiful estate of Twickenham Park under the will of the Countess of Mountrath in 1766, and was promoted lieutenant-general on 30 April 1770. His political principles prevented him from applying for a command in the American war of independence, but he was promoted general on 20 Nov. 1782, and made a field-marshal on 30 July 1796. He died at Twickenham, unmarried, on 21 Oct. 1803, at the age of seventy-four, leaving the bulk of his immense property to his favourite nephew, Lord George Cavendish, M.P., afterwards first earl of Burlington.